Packages containing explosives shipped from Yemen to two synagogues in Chicago have been detected in at least two global locations.

The packages, who were supposedly sent by Al Qaeda terrorists, were found in the UK and the UEA thanks to intelligence information provided by US allies in the Middle East that were not revealed, CNN reported.

US President Barack Obama made a special statement about the terrorist threat alert saying this was a "credible threat" against the USA, as the packages contained explosive material.

"We also know that al Qaeda in the Arabian Peninsula continues to plan attacks against our homeland, our citizens, and our friends and allies," he said during a press briefing on the incident.

The packages originated in Yemen, which is regarded as an Al Qaeda stronghold in the Arabian Peninsula.

CNN cites officials as revealing that the package found on a plane at the East Midlands Airport in the UK contained a "manipulated" toner cartridge and had white powder on it as well as wires and a circuit board.

The terrorist threat alert led US authorities to search 13 other packages from Yemen. Reports say the threat could be a "dry run" on part of Al Qaeda to test the security levels of the USA and its allies.

A senior FBI official has announced that no explosive devices have been on the transport airplanes searched in Chicago.

Meanwhile, an airplane of the Emirates airline flying from the Yemen to JFK, New York, via London, was escorted by US fighter jets from Canadian terrotory as a precaution even though the plane had been searched in the UK.